Polizeidirektion Sachsen-Anhalt Süd said the manipulated yoghurt products were found in supermarkets in Halle (Saale) and Bitterfeld in Sachsen-Anhalt.
They were informed that individual yoghurts of the Ehrmann brand had been contaminated.
A 42-year-old suspect was interrogated after reporting the incident to police on Friday but he has not been charged.
Authorities said in one case a ‘harmful substance’ was found that had been introduced into the product from the outside and damaged the outer packaging. German media reported it was hydrogen peroxide.
They asked consumers to pay particular attention to damage to product packaging. If suspicious products are identified, consumers are asked to inform the salesperson immediately.
Ehrmann said the affected products were delivered without any problems and could only have been manipulated in the market.
Last month, police arrested a man they believe contaminated products and put them on shelves in Friedrichshafen markets to extort money. They seized five glasses of baby food that contained ethylene glycol.